This research project focuses on procedures which will explain, at a molecular level, intercellular recognition and adhesion. We have used the adhesion of cells from embryonic chick liver as a first approach. Using tissue specific antisera directed against chick liver cells, which bind to and block cell:cell adhesion, we have been able to isolate liver adhesion molecules (LAM) from the cell membranes. The antisera were prepared in rabbits and mice by injection of liver cells of purified LAM. We have also prepared hybridomas which secrete anti-LAM. Such monoclonal antisera will be used in future research to develop radioimmune assays for LAM and the detection of LAM during early stages of embryonic development. Characterization of LAM on a physical and chemical basis and its role in cell:cell adhesion is a major aspect of our ongoing research. In addition to the embryonic chick liver systems, we are using similar procedures to investigate the interaction of cells from embryonic rat and mouse liver, and from hepatomas derived from rat. It is hoped that these studies will lead to some understanding of the molecular basis of cell:cell recognition and adhesion in normal development and alterations during malignancy.